JP3914817B2 - Charged particle beam writing method - Google Patents

Description

[0001]
[Field of the Invention]
The present invention relates to a charged particle beam writing method for drawing a desired pattern on a mask substrate or a silicon wafer by an electron beam or an ion beam.
[0002]
[Prior art]
In a variable area type electron beam lithography apparatus that deflects an electron beam while changing the cross-sectional shape of the electron beam applied to the material to be drawn, and draws a desired pattern, the electron beam generated from the electron gun is rectangular. A first slit having an opening is irradiated, and an electron beam transmitted through the first slit is irradiated to a second slit having a rectangular opening.
[0003]
An electron beam having an arbitrary cross-sectional area can be formed by arranging a shaping deflector between the first slit and the second slit and deflecting the electron beam transmitted through the first slit. FIG. 1 shows the relationship between the electron beam EB (L1) transmitted through the rectangular opening L1 (not shown) of the first slit and the rectangular opening L2 of the second slit. By changing the irradiation position of the electron beam EB on the second slit L2 by the shaping deflector, the electron beam K having an arbitrary rectangular cross-sectional area shown by oblique lines can be shaped.
[0004]
By irradiating the material to be drawn with the shaped electron beam and arbitrarily deflecting the electron beam with the positioning deflector, an arbitrary pattern can be drawn on the material to be drawn. When the shaped electron beam is deflected, the deflection distortion cannot be ignored if the deflection angle is increased. For this reason, the drawing area is divided into ranges (fields) in which the deflection distortion of the electron beam can be ignored, the drawing material is moved in units of fields, and a desired pattern is drawn for each field.
[0005]
By the way, in recent years, the design rules for pattern drawing have become increasingly smaller. With this miniaturization, correction processing is performed for the proximity effect that adversely affects pattern drawing accuracy. The proximity effect is a phenomenon in which, when an electron beam irradiated to a material to be drawn is diffused in the material and there is a close pattern, electrons diffused to each other influence each other and a desired drawing accuracy cannot be obtained.
[0006]
For this reason, this proximity effect correction processing is performed. As an example of this proximity effect correction processing, the electron beam drawing area is subdivided, the area of the drawing pattern included in the subdivided area is obtained, and the shot time of the electron beam on the material is controlled according to this area. The proximity effect is corrected. That is, when the pattern area per subdivided unit area is large, the electron beam shot time is shortened, and when the pattern area is equal to or smaller than a certain area, the normal shot time is set. When the proximity effect is corrected more precisely, not only the pattern area of a specific subdivided unit area but also the pattern area of a subdivided area around the pattern area is used for controlling the shot time. Be considered.
[0007]
[Problems to be solved by the invention]
The proximity effect correction process described above can greatly contribute to improving the accuracy of pattern drawing, but it has been found that if the pattern drawing design rule is further miniaturized, various phenomena other than the proximity effect adversely affect the miniaturization. It was. This phenomenon is, for example, a loading effect, a foggy effect, or a resist heating effect.
[0008]
The loading effect refers to the pattern density in the plane of the plate (the material to be drawn) (that is, the density of the workpiece) after the pattern is drawn with the electron beam and then transferred from the development process to the etching process. This is a phenomenon in which the etching rate changes due to the difference. The influence range of the loading effect ranges from several tens of μm to several hundreds of μm.
[0009]
The foggy effect is a phenomenon in which reflected electrons on the plate are reflected by various members in the electron beam column and re-enter the resist surface of the drawing material. The influence range of the foggy effect is several tens of mm.
[0010]
The resist heating effect is a phenomenon in which the drawing material is heated by irradiating the drawing material with an electron beam, and as a result, the sensitivity of the resist changes. When the sensitivity of the resist changes, the developed pattern dimension does not become as designed even if the development process is performed under appropriate conditions. The influence range of the resist heating effect is several μm to several tens of μm. As a typical example of the resist heating phenomenon, when drawing a line or the like, only the line based on the first shot of drawing can be thinned.
[0011]
As described above, in the electron beam or ion beam drawing apparatus, even if only the proximity effect correction processing is performed, there is a limit to the miniaturization of pattern drawing, and in order to further miniaturize the drawing processing, a loading effect is required. To cope with the foggy effect and resist heating effect.
[0012]
The present invention has been made in view of the above-described points, and an object thereof is to realize a charged particle beam writing method that can cope with further miniaturization of pattern drawing in addition to proximity effect correction. .
[0013]
[Means for Solving the Problems]
  In the charged particle beam drawing method according to the first aspect of the present invention, a charged particle beam is shot on a drawing material in accordance with pattern data to be drawn, a desired pattern is drawn on the drawing material, and a drawing region is defined. Virtually divided, the area of the drawing pattern included in the divided areaProximity effect correction amount was calculated, and the correction amount was taken into accountIn a charged particle beam drawing method in which a shot time of a charged particle beam is obtained, a charged particle beam is shot on the divided region at this shot time, and a desired pattern is drawn, the divided region is actually applied to the divided region. Not drawn, but used to determine shot timeThe special pattern data is added to the drawing pattern data included in the divided area, and the proximity effect correction amount in the area is obtained from the area of the drawing pattern to which the special pattern is added.It is characterized by doing so.
Here, the special pattern is pattern data that is not actually drawn in a divided area but is used for obtaining a shot time.
[0014]
  In the first aspect of the present invention, for the proximity effect correction, the drawing area is virtually divided, and the area of the drawing pattern included in the divided area is determined in the area.Proximity effect correction amount was calculated, and the correction amount was taken into accountIn a charged particle beam drawing method in which a shot time of a charged particle beam is obtained, a charged particle beam is shot on the divided region at this shot time, and a desired pattern is drawn, the divided region is actually applied to the divided region. Not drawn, but used to determine shot timeThe special pattern data is added to the drawing pattern data included in the divided area, and the proximity effect correction amount in the area is obtained from the area of the drawing pattern to which the special pattern is added.I did it.
[0015]
  Claim2In the charged particle beam drawing method according to the invention, the charged particle beam is shot on the drawing material according to the pattern data to be drawn, the desired pattern is drawn on the drawing material, and the drawing region is virtually Divide and within the area from the area of the drawing pattern included in the divided areaProximity effect correction amount was calculated, and the correction amount was taken into accountIn a charged particle beam drawing method in which a shot time of a charged particle beam is obtained, a charged particle beam is shot on the divided region at this shot time, and a desired pattern is drawn, the divided region is actually applied to the divided region. Not drawn, but used to determine shot timeA special pattern having an area for adding special pattern data to the drawing pattern data included in the divided area and correcting the influence of resist heating on the first part of each drawing pattern in the divided area And the proximity effect correction amount in the region is calculated from the area of the drawing pattern to which both the special patterns are added.It is characterized by that.
[0016]
  Claim2In the described invention, the drawing area is virtually divided for the proximity effect correction, and the area of the drawing pattern included in the divided area is determined in the area.Obtaining the proximity effect correction amount, further obtaining the shot time of the charged particle beam in consideration of the correction amount, and shot the charged particle beam in the divided area in this shot time,Special pattern data that is not actually drawn in the divided area but is used to determine the shot timeAdd to the drawing pattern data included in the divided area, and add a special pattern having an area for correcting the influence of resist heating to the first part of each drawing pattern in the divided area, A proximity effect correction amount in the region is obtained from the area of the drawing pattern to which both the special patterns are added.I did it.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 2 shows an example of a variable area electron beam lithography apparatus for carrying out the present invention. Reference numeral 1 denotes an electron gun that generates an electron beam EB. The electron beam EB generated from the electron gun 1 is irradiated onto the first shaping slit 3 through the irradiation lens 2.
[0018]
The opening image of the first shaping slit is formed on the second shaping slit 5 by the shaping lens 4, and the position of the image formation can be changed by the shaping deflector 6. The image formed by the second shaping slit 5 is irradiated on the drawing material 9 through the reduction lens 7 and the objective lens 8. The irradiation position on the drawing material 9 can be changed by the positioning deflector 10.
[0019]
Reference numeral 11 denotes a control CPU. The control CPU 11 transfers pattern data from the pattern data memory 12 to the high-speed data control unit 13. The pattern data from the control unit 13 is subjected to necessary data conversion and the like, and each pattern data is supplied to the shot division unit 14.
[0020]
The shot division unit 14 divides the pattern data based on a certain rule. Each shot data divided by the shot dividing unit 14 includes a control circuit 16 including a DA converter and an amplifier for controlling the shaping deflector 6, a control circuit 17 including a DA converter and an amplifier for controlling the positioning deflector 10, and a shot. Via a time control unit 18, the blanker is supplied to a blanker control circuit 20 that controls a blanker (blanking electrode) 18 that blanks the electron beam generated from the electron gun 1. The objective lens 8 is controlled by the objective lens control circuit 21. Further, the control CPU 11 controls the drive circuit 23 of the stage 22 on which the material 9 is placed in order to move the drawing material 9 for each field. The field refers to a region where a pattern is drawn only by electron beam deflection.
[0021]
Reference numeral 24 denotes a proximity effect correction unit. The proximity effect correction unit 24 virtually divides pattern data into small areas, and stores a correction amount of shot time for each small area. The operation of such a configuration will be described next. The voltage is supplied to a control circuit 16 that controls the applied voltage and a blanker control circuit 18 that controls a blanker (blanking electrode) 17 that blanks the electron beam generated from the electron gun 1.
[0022]
Further, the control CPU 11 controls the drive circuit 21 of the stage 20 on which the material 9 is placed in order to move the material 9 for each field. Although not shown, a laser interferometer is provided in the stage portion to measure the amount of movement of the stage. The operation of such a configuration will be described next.
[0023]
First, a basic drawing operation will be described. The pattern data stored in the pattern data memory 12 is sequentially read and supplied to the high-speed data control unit 13. The high-speed data control unit 13 performs processing such as pattern data conversion, and each data is supplied to the shot division unit 14.
[0024]
The shot division unit 14 divides pattern data based on a predetermined division rule. Based on the divided pattern data, the deflection control circuit 16 controls the shaping deflector 6 and the control circuit 17 controls the positioning deflector 10.
[0025]
As a result, the cross section of the electron beam is formed into a unit pattern shape by the shaping deflector 6 based on each pattern data, and the unit pattern is sequentially shot on the material 9 to perform pattern drawing of a desired shape. At this time, blanking of the electron beam is executed in synchronization with a shot of the electron beam on the material 9 by a blanking signal from the blanker control circuit 18 to the blanker 17. The shot time at this time is adjusted by the shot time control unit 18, and this operation will be described later.
[0026]
Further, when drawing on different regions (fields) on the material 9, the stage 22 is moved by a predetermined distance according to a command from the control CPU 11 to the stage drive circuit 23. Although the moving distance of the stage 22 is not shown, it is monitored by a laser length measuring device, and the position of the stage is accurately controlled based on the length measurement result from the length measuring device.
[0027]
Now, in the drawing for each shot, the shot time of the electron beam is controlled to correct the proximity effect. This operation will be described next. The proximity effect correction unit 24 virtually divides pattern data into small areas in advance, and stores shot time correction values according to the density of patterns included in each divided area (= total area of patterns). ing.
[0028]
This correction value is set so that the shot time is relatively short when the density of the patterns included in the divided small regions is high, that is, when the total area of the patterns is large, and conversely, When the density of the pattern included in the small area is low, that is, when the total area of the pattern is small, the shot time is set to a relatively long value.
[0029]
The proximity effect correction unit 24 reads the correction value of the shot time from the coordinate value of the rectangular pattern divided by the shot division unit 14 and supplies it to the shot time control unit 18. As a result, the blanking signal to the blanker 19 is controlled so that the electron beam is shot on the material 9 for the time required for correcting the proximity effect.
[0030]
Next, a case where loading effect correction is performed will be described. As described above, the loading effect is drawn into an etching process after drawing a pattern with an electron beam. In this process, due to the difference in pattern density in the plate surface (that is, the density of the workpiece), This is a phenomenon in which the etching rate changes. That is, if the pattern density in the unit is high, the reaction solution becomes thin and the reaction rate becomes slow, so that the etching cannot be performed sufficiently. The influence range of the loading effect ranges from several tens of μm to several hundreds of μm.
[0031]
In order to correct such a loading effect, the following preparation is made before the drawing operation is performed. First, the pattern data is divided into designated unit sizes (for example, a small area of 10 × 10 μm is called a unit). This unit is equivalent to a small area virtually divided for the above-described proximity effect correction. The loading correction amount in the divided unit is obtained by calculating a pattern area existing within a specified radius (for example, 50 μm) from the own unit.
[0032]
Based on the calculated pattern area, the line width correction amount is obtained by a conversion formula of the pattern area ratio to the line width correction amount obtained in advance. FIG. 3 shows a relationship between the line width variation amount characteristic f with respect to the pattern area ratio and the line width correction amount characteristic (a characteristic opposite to f) f ′. From the thus obtained line width correction amount (loading correction amount), the correction time of the electron beam shot time is obtained. The relationship between the correction time of the electron beam shot time with respect to the line width correction amount is obtained in advance.
[0033]
The correction time described above is obtained by calculation for each unit, and pseudo pattern data having a magnitude that gives the amount of reflected electrons sufficient to correct the line width change due to the loading effect is created from the calculated correction time. This pseudo pattern data is added to the actual pattern data, but this pseudo pattern is used for calculating the proximity effect correction amount, and a special command is added to the pseudo pattern data so that it is not actually shot. ing.
[0034]
The creation of the pseudo pattern and the addition of the pseudo pattern data to the actual pattern data are executed prior to the actual drawing operation. FIG. 4 shows an example of a unit in which a pseudo pattern is added to a real pattern. The hatched patterns surrounded by a solid line are real patterns R1 and R2, and the pattern shown by a dotted line is a pseudo pattern. S. In FIG. 4, the pseudo pattern is added to an area where the actual pattern does not exist. However, since this pseudo pattern is not actually drawn, a part or all of the pseudo pattern may be added to overlap with the actual pattern.
[0035]
After the preprocessing as described above is performed, if the pattern data to which the pseudo pattern data is added is supplied from the pattern data memory 12 to the proximity effect correction unit 24 via the control CPU 11, the pattern data is obtained by the correction unit 24. Based on the above, the shot time of the electron beam is obtained by calculation. The electron beam shot time obtained by the proximity effect correction unit 24 is supplied to the control unit 18. As a result, the blanking signal to the blanker 19 is controlled such that the electron beam EB is shot on the material 9 for the time required for correcting the proximity effect and the loading effect.
[0036]
Next, an operation for correcting the foggy effect will be described. As described above, the foggy effect is a phenomenon in which reflected electrons on the plate are reflected by various members in the electron beam column and re-enter the resist surface of the drawing material. The influence range of this foggy effect is several tens of mm.
[0037]
In order to correct such a foggy effect, a drawing area is virtually divided into unit units (for example, 1 × 1 mm), a pattern area in the unit unit is calculated, and an influence curve (pattern position pair) obtained in advance is calculated. The irradiation correction amount for each unit unit is obtained according to (line width). A special pattern that provides this irradiation correction amount is added to the original pattern data. In this case, it is desirable to give one special pattern to a minute section (for example, 10 × 10 μm) so that the correction amount in the unit unit is substantially constant.
[0038]
After the preprocessing as described above is performed, if pattern data to which a special pattern is added is supplied from the pattern data memory 12 to the proximity effect correction unit 24 via the control CPU 11, the correction unit 24 converts the pattern data into pattern data. Based on this, the shot time of the electron beam is obtained by calculation. The shot time of the electron beam obtained by the proximity effect correction unit 24 is supplied to the shot time control unit 18. As a result, the blanking signal to the blanker 19 is controlled such that the electron beam EB is shot on the material 9 for the time required for correcting the proximity effect and the foggy effect.
[0039]
Next, a case where resist heating correction is performed will be described. Resist heating is a phenomenon in which the material to be drawn is heated by irradiating the material to be drawn with an electron beam, and as a result, the sensitivity of the resist changes. When the sensitivity of the resist changes, the developed pattern dimension does not become as designed even if the development process is performed under appropriate conditions. The influence range of the resist heating effect is several μm to several tens of μm. As a typical example of this resist heating phenomenon, when drawing a line or the like, only the line based on the first shot of drawing is thinned (relative sensitivity is not affected by the heat of other shots). Can be reduced).
[0040]
In order to correct this resist heating effect, a special pattern that increases the shot time of the electron beam shot to the first part of each drawing pattern by the required amount (only for calculation of accumulated scattered electron quantity, that is, dose calculation) Used, not actually shot). At the time of actual drawing, the shot time corresponding to the special pattern position is adjusted by the influence of the resist heating effect.
[0041]
FIG. 6 shows an example of a unit in which a special pattern is added to an actual pattern. T is a real pattern and U is a special pattern. In FIG. 6, U acts to reduce the amount of scattered electrons in the calculation of scattered electrons in the proximity effect correction unit.
[0042]
In the first embodiment described above, for each virtually divided small region (unit), a pseudo pattern that is not drawn in the actual pattern but is used for the calculation of the pattern area is added, and proximity effects and loading are added. A method for correcting the effect will be described. In the second embodiment, a method similar to that in the first embodiment, that is, drawing in an actual pattern for each virtually divided small area (unit). Although the method of correcting the proximity effect and the foggy effect by adding a pseudo pattern to be used for the calculation of the pattern area has been explained, the size of the pseudo pattern can be adjusted to correct both the loading effect and the foggy effect at the same time. For example, the proximity effect, loading effect, and foggy effect can be corrected simultaneously.
[0043]
In addition, a pseudo pattern of a size that simultaneously corrects both the loading effect and the foggy effect is added, and the proximity effect, the loading effect, and the foggy effect are corrected at the same time. If a special pattern that increases by a necessary amount is added, the resist heating correction can be performed simultaneously.
[0044]
Although the embodiments of the present invention have been described above, the present invention is not limited to these embodiments. For example, the electron beam drawing method has been described as an example, but the present invention can also be applied to an ion beam drawing apparatus.
[0045]
【The invention's effect】
  As described above, in the charged particle beam drawing method according to the first aspect of the present invention, a charged particle beam is shot on a drawing material in accordance with pattern data to be drawn, and a desired pattern is drawn on the drawing material. And virtually divide the drawing area, and from the area of the drawing pattern included in the divided area,Proximity effect correction amount was calculated, and the correction amount was taken into accountIn a charged particle beam drawing method in which a shot time of a charged particle beam is obtained, a charged particle beam is shot on the divided region at this shot time, and a desired pattern is drawn, the divided region is actually applied to the divided region. Not drawn, but used to determine shot timeThe special pattern data is added to the drawing pattern data included in the divided area, and the proximity effect correction amount in the area is obtained from the area of the drawing pattern to which the special pattern is added.I did it.
[0046]
  As a result, in the first aspect of the present invention, in order to correct the proximity effect, the drawing area is virtually divided, and the shot of the charged particle beam in the area is calculated from the area of the drawing pattern included in the divided area. Pattern data that is used to calculate the shot time, but is not actually drawn in the divided area with this shot time.(Special pattern data)Thus, the loading effect and the foggy effect can be corrected, and the drawing process can be further miniaturized.
[0047]
  Claim2In the charged particle beam drawing method according to the invention, the charged particle beam is shot on the drawing material according to the pattern data to be drawn, the desired pattern is drawn on the drawing material, and the drawing region is virtually Divide and within the area from the area of the drawing pattern included in the divided areaObtain the proximity effect correction amount, and further determine the shot time of the charged particle beam in consideration of the correction amount,In a charged particle beam drawing method in which a charged particle beam is shot on the divided area in this shot time and a desired pattern is drawn, in order to obtain the shot time, although not actually drawn in the divided area. Special pattern data used forIs added to the drawing pattern data included in the divided area, and a special pattern having an area for correcting the influence of resist heating is added to the first part of each drawing pattern in the divided area. The proximity effect correction amount in the region is obtained from the area of the drawing pattern to which both the special patterns are added.It is characterized by that.
[0048]
  Claim2In the described invention, the drawing area is virtually divided for the proximity effect correction, and the area of the drawing pattern included in the divided area is determined in the area.Obtaining the proximity effect correction amount, further obtaining the shot time of the charged particle beam in consideration of the correction amount, and shot the charged particle beam in the divided area in this shot time,Although it is not actually drawn in the divided area, it is used to calculate the shot time.A special pattern having an area for adding special pattern data to the drawing pattern data included in the divided area and correcting the influence of resist heating on the first part of each drawing pattern in the divided area And the proximity effect correction amount in the region is obtained from the area of the drawing pattern to which both the special patterns are added.As a result, for example, when drawing a line or the like, a phenomenon in which only the line based on the first shot of drawing is thinned is prevented.
[Brief description of the drawings]
FIG. 1 is a diagram for explaining the principle of shaping an electron beam having a variable area.
FIG. 2 is a diagram showing an example of an electron beam drawing apparatus for carrying out the present invention.
FIG. 3 is a diagram illustrating a relationship between a line width variation amount characteristic f with respect to a pattern area ratio and a line width correction amount characteristic (a characteristic opposite to f) f ′.
FIG. 4 is a diagram illustrating an example of a unit in which a pseudo pattern is added to an actual pattern.
FIG. 5 is a diagram illustrating a relationship between an area ratio and a line width variation amount due to a foggy effect.
FIG. 6 is a diagram illustrating an example of a unit in which a special pattern is added to an actual pattern.
[Explanation of symbols]
1 electron gun
2 Irradiation lens
3 1st slit
4 Molded lens
5 Second slit
6 Forming deflector
7 Reduction lens
8 Objective lens
9 Drawing material
10 Positioning deflector
11 Control CPU
12 Pattern data memory
13 Data transfer circuit
14 Molding deflector control circuit
15 Positioning deflector control circuit
16 Objective lens control circuit
17 Blanker
18 Blanker control circuit
20 stages
21 Stage drive circuit

Claims (5)

A charged particle beam is shot on the drawing material according to the pattern data to be drawn, and a desired pattern is drawn on the drawing material, and the drawing area is virtually divided, and the drawing included in the divided area The proximity effect correction amount in the region is calculated from the area of the pattern , and the shot time of the charged particle beam is calculated in consideration of the correction amount, and the charged particle beam is shot in the divided region with this shot time, In the charged particle beam drawing method for drawing a pattern, drawing pattern data that is not actually drawn in the divided area but includes special pattern data used for obtaining a shot time is included in the divided area. The proximity effect correction amount in the region is obtained from the area of the drawing pattern to which the special pattern is added. A charged particle beam drawing method so. A charged particle beam is shot on the drawing material according to the pattern data to be drawn, and a desired pattern is drawn on the drawing material, and the drawing area is virtually divided, and the drawing pattern included in the divided area The proximity effect correction amount in the area is calculated from the area of the area, and the shot time of the charged particle beam is calculated by taking the correction amount into consideration, and the charged particle beam is shot in the divided area with the shot time, and the desired pattern is obtained. In the charged particle beam drawing method that draws, the special pattern data that is not actually drawn in the divided area but is used for obtaining the shot time is used as the drawing pattern data included in the divided area. In addition, the effect of resist heating is added to the first part of each drawing pattern in the divided area. Add a special pattern having an area for the two special pattern added was from the area of the drawing pattern to determine the proximity effect correction amount in the region charged particle beam writing method. The are not actually drawn, the special pattern data used to determine the shot time, the charged particle beam writing method of claim 1 or 2, wherein there is a size area for correcting the loading effect. The are not actually drawn, the shot special pattern data used to determine the time, the charged particle beam writing method of claim 1 or 2, wherein there is a size area to correct a full Ogi effect . 3. The charged particle according to claim 1, wherein the special pattern data which is not actually drawn but is used for obtaining the shot time is an area having a size for correcting both the loading effect and the foggy effect. Beam drawing method.

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